Electrical and Interfacial Properties of GaAs MOS Capacitors With La-Doped ZrON as Interfacial Passivation Layer

GaAs MOS capacitors with ZrTiON high-k gate dielectric and ZrLaON or ZrON as interfacial passivation layer (IPL) are fabricated, and their electrical properties are investigated. As compared with a control sample without IPL, improved interfacial quality and electrical properties are obtained for both samples, with the ZrTiON/ZrLaON/GaAs device, exhibiting the lowest interface-state density (1.1 × 10
¹²
cm
^-2
eV
^-1
), smallest gate leakage current density (1.62 × 10
^-5
A cm
^-2
at V
_g
= V
_fb
+ 1 V), and largest equivalent dielectric constant (25.1). All of these should be attributed to the fact that incorporating La into the ZrON IPL can: first, passivate its defects and, second, enhance the blocking role of the IPL against the Ti/O in-diffusion to the GaAs substrate and the Ga/As out-diffusion to the high-k, thus resulting in an obvious reduction of relevant defects in the gate stack and also suppressing the formation of unstable Ga/As oxides and As-As dimer at the GaAs surface to obtain a much improved dielectric/GaAs interface.